Optical or photoelectric sensors use light to sense targets without physical contact and are used in a wide variety of applications and environments, such as to sequentially detect the presence or absence of targets on a conveyor belt. Various types of optical sensors are available, such as light curtains, transmitted beam sensors, retro-reflective sensors, and diffuse sensors. Typically, each of these sensors includes a light source, such as a light emitting diode (LED) or a laser, and a photodetector for detecting light, such as a photodiode or phototransistor, and can also include one or more lenses to focus or narrow the beam of light emitted by the light source and/or to focus or narrow the received light for efficient detection by the photodetector. These sensors typically also include circuitry in communication with the photodetector for producing a voltage or current signal indicative of a characteristic of the sensed target, such as high and low voltage or current states for respectively indicating the presence and the absence of the target at a specified location.
The accurate sensing of targets can be rendered difficult under various conditions such as when the signal-to-noise ratio is very low. For example, some photoelectric sensors have limited ability to function reliably in the presence of various types of environmental noise, signals from other sensors, and/or interference from unintended targets, such as lambertian surfaces. In such circumstances, a given optical sensor can misconstrue one or more other signals (unintended signals, e.g., noise) as intended signals, and therefore generating a false detection within the sensor. In an effort to accommodate these issues, sensors are often detuned or otherwise modified to limit their capabilities in order to avoid detecting unwanted signals. Such modifications can often render the sensor substantially unsuitable for its intended use. For example, limiting the sensing range of a sensor to prevent sensing other adjacent signals can be too constricting for a particular process that requires longer range sensing. In other cases, to accommodate limited sources of noise, techniques involving modification of the transmitter and/or receiver channels have been attempted, but these techniques have proven to be expensive and have met with very limited success.
In addition, when one or more sensors are within another sensor's field of view, cross-talk can occur, rendering the sensors unreliable and requiring changes to the physical placement of various components in processes to attempt to accommodate the sensors' limitations. This can be a particular problem in manufacturing processes that often require numerous sensors to be located adjacent to each other on a single conveyor or across from each other on different conveyors.
Therefore, it would be advantageous if an improved system or method for use in relation to optical sensing systems and/or methods could be developed that would allow one or more of the drawbacks discussed above to be entirely or at least partly overcome.